Comparative clinical effects of hydromorphone and morphine: a meta-analysis

We have conducted a meta-analysis of the clinical effects of morphine and hydromorphone to compare their benefit in analgesia. Embase and Medline were searched with an end-date of June 2009 for randomized, controlled trials or observational studies that addressed comparative analgesic and side-effects or particular side-effects. Two researchers independently identified included studies and extracted the data. Estimates of opioid effects were combined by using a random-effects model. Meta-analysis of eight studies suggested that hydromorphone (494 patients) provides slightly better (P=0.012) clinical analgesia than morphine (510 patients). The effect-size was small (Cohen's d=0.266) and disappeared when one study was removed, although the advantage of hydromorphone was more evident in studies of better quality (Jadad's rating). Side-effects were similar, for example, nausea (P=0.383, nine studies, 456 patients receiving hydromorphone and 460 morphine); vomiting (P=0.306, six studies, 246 patients receiving hydromorphone and 239 morphine); or itching (P=0.249, eight studies, 405 patients receiving hydromorphone, 410 morphine). This suggests some advantage of hydromorphone over morphine for analgesia. Additional potential clinical pharmacological advantages with regard to side-effects, such as safety in renal failure or during acute analgesia titration, are based on limited evidence and require substantiation by further studies.

A locust DNA-binding protein involved in gene regulation by juvenile hormone

Although juvenile hormone (JH) has essential roles in insect development and reproduction, the molecular mechanisms of gene regulation by JH remain an enigma. In Locusta migratoria, the partially palindromic 15-nt sequence, GAGGTTCGAG(A)/(T)CCT(T)/(C), found upstream of a JH-induced gene, jhp21, was designated as a putative juvenile hormone response element (JHRE). When JH-deprived adult female locusts were treated with the active JH analog, methoprene, a fat body nuclear factor that bound specifically to JHRE appeared after 24 h. Binding exhibited a preference for an inverted repeat with GAGGTTC in the left half-site, a single nucleotide spacer, and a right half-site in which some variation is acceptable. Binding to JHRE was abolished by phosphorylation catalyzed by a C-type protein kinase present in the nuclear extracts. The DNA-binding protein is thus believed to be a transcription factor, which is brought to an active state through the action of JH and then participates in the regulation of certain JH-dependent genes.

A microsomal ecdysone-binding cytochrome P450 from the insect Locusta migratoria purified by sequential use of type-II and type-I ligands

A dual-affinity method was established to purify, for the first time, a microsomal ecdysone-binding cytochrome P450 protein from locust Malpighian tubules. This method involved, after prepurification on omega-octylamino-agarose and hydroxylapatite, binding of cytochrome P450 to an immobilized triazole-based general P450 inhibitor (type-II ligand) followed by elution with the substrate ecdysone (type-I ligand) of the bound cytochrome. The isolated material showed a typical cytochrome P450 spectrum, a specific heme content of 13 nmol/mg protein, and a prominent protein of about 60 kDa on SDS-PAGE. Based on a tryptic undecapeptide sequence the isolated protein may be identical to CYP6H1, a putative ecdysone 20-monooxygenase recently cloned from the same tissue. Ecdysone 20-monooxygenase activity could be partially reconstituted from microsomal detergent extracts, when supplemented with purified bovine cytochrome P450 reductase and detergent-extracted microsomes; reconstitution was not successful with any chromatographic fraction, however. Therefore, purification of the locust cytochrome P450 was monitored by ecdysone-induced type-I difference spectra, whenever applicable, in addition to carbon monoxide spectra. Affinity columns with matrix-bound diethylstilbestrol and testosterone 3-thiosemicarbazone, but not with the 17beta-hemisuccinate, yielded elution profiles with ecdysone that were comparable to those of the triazole matrix. The concept of dual-affinity chromatography described here may be generally applicable to the isolation of cytochromes P450.

Chemistry and biology of thiamethoxam: a second generation neonicotinoid

Thiamethoxam is the first commercial neonicotinoid insecticide from the thianicotinyl subclass. It was discovered in the course of our optimisation program on neonicotinoids started in 1985. Novel variations of the nitroimino-heterocycle of imidacloprid led to 4-nitroimino-1,3,5-oxadiazinanes exhibiting high insecticidal activity. Among these, thiamethoxam (CGA 293433) was identified as the best compound and selected for worldwide development. The compound can be synthesised in only a few steps and high yield from easily accessible starting materials. Thiamethoxam acts by binding to nicotinic acetylcholine receptors. It exhibits exceptional systemic characteristics and provides excellent control of a broad range of commercially important pests, such as aphids, jassids, whiteflies, thrips, rice hoppers, Colorado potato beetle, flea beetles and wireworms, as well as some lepidopteran species. In addition, a strong preventative effect on some virus transmissions has been demonstrated. Thiamethoxam is developed both for foliar/soil applications and as a seed treatment for use in most agricultural crops all over the world. Low use rates, flexible application methods, excellent efficacy, long-lasting residual activity and favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.

Metabolism of diafenthiuron by microsomal oxidation: procide activation and inactivation as mechanisms contributing to selectivity

The thiourea insecticide/acaricide diafenthiuron represents a biologically inactive propesticide that requires transformation into the active carbodiimide derivative. The carbodiimide inhibits mitochondrial respiration by selective and covalent binding to the proteolipid (8 kDa) of Fo-ATPase in the inner membrane and to porin (30 kDa) in the outer membrane. The thiourea can be activated by light as well as by cytochrome P450 in the insect. To get insight into the enzymatic mechanisms of activation, model in vitro studies were performed using [14C]diafenthiuron and microsomes from various vertebrate livers and from locust Malpighian tubules. Though there was a common set of metabolites, their quantities varies significantly with the species and assay conditions. As a typical product, p-hydroxydiafenthiuron was identified in assay with rat and mouse microsomes. The sulfomonoxide predominated in hen and fish assays, whereas pig and bovine microsomes almost exclusively produced the carbodiimide. The sulfoxide was shown to be a precursor of the carbodiimide. Formation of all metabolites was dependent on the presence of NADPH and active microsomes. The effects of inhibitors and the requirement for NAPDH suggested a role of cytochrome P450-dependent monooxygenase(s) in the formation of both the hydroxylated product and the carbodiimide. FAD-dependent monooxygenases (FMOs) may also be involved in a step following sulfoxidation. These in vitro studies revealed potential mechanisms contributing to biological selectivity of the effects of a pesticide that acts in a non-selective mode at a conserved mitochondrial site.

Photoaffinity labeling of insect nicotinic acetylcholine receptors with a novel [(3)H]azidoneonicotinoid

The nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel in the insect CNS and a target for major insecticides. Here we use photoaffinity labeling to approach the functional architecture of insect nAChRs. Two candidate 5-azido-6-chloropyridin-3-yl photoaffinity probes are evaluated for their receptor potencies: azidoneonicotinoid (AzNN) with an acyclic nitroguanidine moiety; azidodehydrothiacloprid. Compared to their non-azido parents, both probes are of decreased potencies at Drosophila (fruit fly) and Musca (housefly) receptors but AzNN retains full potency at the Myzus (aphid) receptor. [(3)H]AzNN was therefore radiosynthesized at high specific activity (84 Ci/mmol) as a novel photoaffinity probe. [(3)H]AzNN binds to a single high-affinity site in Myzus that is competitively inhibited by imidacloprid and nicotine and further characterized as to its pharmacological profile with various nicotinic ligands. [(3)H]AzNN photoaffinity labeling of Myzus and Homalodisca (leafhopper) detects a single radiolabeled peak in each case displaceable with imidacloprid and nicotine and with molecular masses corresponding to approximately 45 and approximately 56 kDa, respectively. The photoaffinity-labeled receptor in both Drosophila and Musca has imidacloprid- and nicotine-sensitive profiles and migrates at approximately 66 kDa. These photoaffinity-labeled polypeptides are considered to be the insecticide-binding subunits of native insect nAChRs.

5-Azidoimidacloprid and an acyclic analogue as candidate photoaffinity probes for mammalian and insect nicotinic acetylcholine receptors

The 5-azido analogue of the major insecticide imidacloprid, 1-(5-azido-6-chloropyridin-3-ylmethyl)-2-nitroiminoimidaz olidine (1), and an acyclic analogue, N-(5-azido-6-chloropyridin-3-ylmethyl)-N'-methyl-N' '-nitroguanidine (2), were prepared in good yields as candidate photoaffinity probes for mammalian and insect nicotinic acetylcholine receptors (nAChRs). The essential intermediate was 5-azido-6-chloropyridin-3-ylmethyl chloride (3) prepared in two ways: from 6-chloro-5-nitronicotinic acid by selective reduction and then diazotization, and from N-(6-chloropyridin-3-ylmethyl)morpholine by an electrophilic azide introduction with lithium diisopropylamide followed by chlorine substitution of morpholine with ethyl chloroformate. Coupling of 3 with 2-nitroiminoimidazolidine gave 1. Conversion of 3 to 2 was achieved in good yields via the hexahydrotriazine intermediate 14. Fortuitously, the azido substituent in 1 and 2 increases the affinity 7-79-fold for rat brain and recombinant alpha4beta2 nAChRs (K(i)s 4.4-60 nM competing with [(3)H](-)-nicotine) while maintaining high potency on both insect nAChRs (Drosophila and Myzus) (K(i)s 1-15 nM competing with [(3)H]imidacloprid). Azidopyridinyl compounds 1 and 2 are therefore candidate photoaffinity probes for characterization of both mammalian and insect receptors.

Candidate target mechanisms of the growth inhibitor cyromazine: studies of phenylalanine hydroxylase, puparial amino acids, and dihydrofolate reductase in dipteran insects

Cyromazine, an insect growth regulator, affects larval and pupal cuticles in dipterans and some other insects. The mode of action of this aminotriazine is not known yet, though it has been shown not to inhibit the synthesis of chitin and cuticular proteins. Cyromazine may, however, act on some step(s) of sclerotization of the cuticle. In the present study, we have analyzed the key enzyme for the production of sclerotization agents, phenylalanine hydroxylase (PAH), using the enzyme from Drosophila, a cyromazine-sensitive insect. PAH was studied in vitro with cyromazine and three biologically less active derivatives at concentrations ranging from 1 microM to 1 mM. None of the compounds did significantly affect PAH activity. Nor did cyromazine, fed to last instar larvae of Musca domestica, change the relative content of phenylalanine and tyrosine, or the total amount and profile of amino acids of puparial cuticles, which showed a larviform shape typical for cyromazine intoxication. Taken together, this study does not support the hypothesis that phenylalanine hydroxylase represents a target site of cyromazine. In additional studies, the conflicting results, as reported by others, on in vitro inhibition of dihydrofolate reductase (DHFR) by cyromazine were re-examined using the enzymes from larvae of the blowfly, Protophormia terraenovae, and from hen liver. There was no significant inhibition of either DHFR at 100 microM by cyromazine as well as by dicylanil, a pyrimidine analog that is biologically more active than cyromazine. In conclusion, the mode of action of cyromazine remains completely open.

Insect nicotinic acetylcholine receptor: conserved neonicotinoid specificity of [(3)H]imidacloprid binding site

The insect nicotinic acetylcholine receptor (nAChR) is a major target for insecticide action. The rapidly expanding use of neonicotinoid insecticides of varied structures makes it increasingly important to define similarities and differences in their action, particularly for the first-generation chloropyridinyl compounds versus the second-generation chlorothiazolyl derivatives. We have shown with Musca domestica that a convenient and relevant determination of the neonicotinoid insecticide target is a binding site assay with [(3)H]imidacloprid ([(3)H]IMI). This study uses membranes from the aphids MYZUS: persicae and Aphis craccivora and from heads of the flies Drosophila melanogaster and Musca domestica to characterize the [(3)H]IMI binding sites relative to their number and possible species variation in structure-activity relationships. With emphasis on commercial neonicotinoids, six potent chloropyridinyl compounds are compared with the corresponding six chlorothiazolyl analogues (syntheses are given for chemicals prepared differently than previously described). The preference for chloropyridinyl versus chlorothiazolyl is not dependent on the insect species examined but instead on other structural features of the molecule. The chlorothiazolyl substituent generally confers higher potency in the clothianidin and desmethylthiamethoxam series and the chloropyridinyl moiety in the imidacloprid, thiacloprid, acetamiprid, and nitenpyram series. Two chlorothiazolyl compounds compete directly with the chloropyridinyl [(3)H]IMI for the same binding sites in Myzus and Drosophila membranes. This study shows conserved neonicotinoid specificity of the [(3)H]IMI binding site in each of the four insect species examined.

Characterization of nicotinic acetylcholine receptors from the insects Aphis craccivora, Myzus persicae, and Locusta migratoria by radioligand binding assays: relation to thiamethoxam action

Thiamethoxam, a new neonicotinoid insecticide acting at nicotinic acetylcholine receptors, was characterized in competition binding assays with [3-H]-imidacloprid, a specific nicotinic ligand, using membranes from the aphids Aphis craccivora and Myzus persicae, and from the locust Locusta migratoria. In all insects, Scatchard analysis suggested two binding sites for imidacloprid with Kd values in the range of 1 nM and 10 nM, respectively. The Hill values were significantly below 1 (range of 0.63 to 0.85). In contrast to imidacloprid and nicotine, the potency of thiamethoxam to displace [3-H]-imidacloprid varied considerably among these insects. Thiamethoxam was more active than nicotine on Aphis receptors but 100-fold less in Locusta, a nontarget insect. Comparable relations were found to nithiazine. In Myzus, the inhibition curve for thiamethoxam was shallow. This suggested a heterogeneous receptor population displaying a range of binding affinities to thiamethoxam in this aphid. In all three insects, the other neonicotinoid insecticides studied competed with [3-H]-imidacloprid in the same order: thiacloprid > imidacloprid > or = acetamiprid > nitenpyram. N-Methylation of imidacloprid strongly reduced the affinity to the imidacloprid site, whereas N-demethylation of thiamethoxam resulted in a comparable increase of affinity. Supplementary assays were performed with (-)-[3-H]-nicotine and [3-H]-alpha-bungarotoxin on locust membranes. Overall, the data suggested that the outstanding insecticidal properties of thiamethoxam may be due to either a different binding site on nicotinic receptors, or receptor isoforms, or specific pharmakokinetic behavior, rather than to exceptional affinity to one of the examined binding sites.

Characterization of nicotinic acetylcholine receptors from the insects Aphis craccivora, Myzus persicae, and Locusta migratoria by radioligand binding assays: relation to thiamethoxam action

Thiamethoxam, a new neonicotinoid insecticide acting at nicotinic acetylcholine receptors, was characterized in competition binding assays with [3-H]-imidacloprid, a specific nicotinic ligand, using membranes from the aphids Aphis craccivora and Myzus persicae, and from the locust Locusta migratoria. In all insects, Scatchard analysis suggested two binding sites for imidacloprid with Kd values in the range of 1 nM and 10 nM, respectively. The Hill values were significantly below 1 (range of 0.63 to 0.85). In contrast to imidacloprid and nicotine, the potency of thiamethoxam to displace [3-H]-imidacloprid varied considerably among these insects. Thiamethoxam was more active than nicotine on Aphis receptors but 100-fold less in Locusta, a nontarget insect. Comparable relations were found to nithiazine. In Myzus, the inhibition curve for thiamethoxam was shallow. This suggested a heterogeneous receptor population displaying a range of binding affinities to thiamethoxam in this aphid. In all three insects, the other neonicotinoid insecticides studied competed with [3-H]-imidacloprid in the same order: thiacloprid > imidacloprid > or = acetamiprid > nitenpyram. N-Methylation of imidacloprid strongly reduced the affinity to the imidacloprid site, whereas N-demethylation of thiamethoxam resulted in a comparable increase of affinity. Supplementary assays were performed with (-)-[3-H]-nicotine and [3-H]-alpha-bungarotoxin on locust membranes. Overall, the data suggested that the outstanding insecticidal properties of thiamethoxam may be due to either a different binding site on nicotinic receptors, or receptor isoforms, or specific pharmakokinetic behavior, rather than to exceptional affinity to one of the examined binding sites.

Cloning of a cDNA encoding a novel cytochrome P450 from the insect Locusta migratoria: CYP6H1, a putative ecdysone 20-hydroxylase

The biosynthesis of the steroidal molting hormone, 20-hydroxyecdysone, of arthropods involves a series of cytochrome P450-catalyzed hydroxylations. None of the many sequences of insect cytochromes P450, known to date, is related to ecdysteroid pathways. Here, we report the cloning and sequencing of a full-length cDNA of a new cytochrome P450, classified as CYP6H1, from malpighian tubules of the locust, Locusta migratoria. The 1854 bp DNA contained an open reading frame coding for a protein of 542 amino acids, a 5'-leader sequence and a 3'-untranslated region containing a polyadenylation signal and a poly(A) tail. The encoded protein had been isolated as an ecdysone-binding cytochrome P450 from microsomes of the same tissue in previous work. The closest homolog of CYP6H1 was CYP6A2 from Drosophila with 42.1% identity. According to Northern analysis, CYP6H1 is predominantly expressed at larval instars and in malpighian tubules. Evidence is presented for a functional assignment of CYP6H1 to microsomal ecdysone 20-hydroxylase of the locust.

HPLC method for the analysis of acetonides of ecdysteroids providing structural information on different vicinal diols

The polyhydroxy structure of ecdysteroids provides a basis for the formation of various derivatives including the acetonides that have been frequently prepared mainly in preparative work. Acetonides can be formed between vicinal diols in cis position such as positions C-2/C-3 and C-20/C-22 in 20-hydroxyecdysone, for example. We have modified an established procedure for the preparation of acetonides, employing a higher concentration of phosphomolybdic acid as a catalyst, and developed a reverse-phase HPLC method to analyze the products on a micro scale. The derivatization method is fast, taking minutes or less, and does not produce artifacts. Thirteen structurally diverse ecdysteroids were studied in detail concerning speed of acetonide formation, and the number and type of intermediate and end products. Mass spectrometry coupled to HPLC was employed to confirm and/or identify ecdysteroids and their acetonide derivatives. Analysis of the chromatographic profiles revealed that detailed information on vicinal diols of ecdysteroids can be derived from the differences in retention times (Deltar.t.)1 of products relative to the parent steroids on reverse-phase HPLC using a linear water/methanol gradient for elution. The specific Deltar.t. values characterize a product as a monoacetonide, a diacetonide, or a triacetonide. Furthermore, this chromatographic shift upon acetonide formation is significantly different among the various monoacetonides and, thus, specific for the site on the ecdysteroid molecule. The same seems to hold for diacetonides. As variation of the Deltar.t. values for a specific type of acetonide was rather small among the tested ecdysteroids, the results should provide reliable structural information. Muristerone A did not completely fit this common pattern. However, this may specify its uncommon ecdysteroid structure. The method has recently been successfully employed to solve the structures of new ecdysteroid metabolites. Arch. Copyright 1999 Wiley-Liss, Inc.

Comparative studies of suidatrestin, a specific inhibitor of trehalases

Suidatrestin, isolated from a Streptomyces strain, was characterized as a new trehalase inhibitor. Its inhibitory potential was 7 to 50-fold higher than that of validamycin when tested against insect, fungal and mammalian trehalases. The kinetic properties of suidatrestin were studied in vitro with trehalases from flight muscle mitochondria of the fly, Protophormia terraenovae, from larval midgut of the moth, Spodoptera littoralis, and from porcine kidney, as well as with maltase from yeast. Suidatrestin was inactive on maltase but inhibited all trehalases with IC50 values of 0.08-0.1 microM; Ki values ranged from 0.02 to 0.05 microM. The very low Ki/K(m) ratios (3.9 x 10(-6) -4.9 x 10(-6)) indicated excellent in vitro inhibitory action of suidatrestin. When injected into larvae of S. littoralis, suidatrestin required high and repetitive doses which lead to reversible inhibition of larval growth only. Consecutive omission of the inhibitor even stimulated weight increase above that of controls. Significant mortality was achieved at a rather high dose only. Injection of a growth-inhibiting dose of suidatrestin did not change hemolymph osmolality as a measure of sugar concentration. The discrepancy between in vitro and in vivo potency of suidatrestin may be understood once its chemical structure is fully known.

26-hydroxylation of ecdysteroids is catalyzed by a typical cytochrome P-450-dependent oxidase and related to ecdysteroid resistance in an insect cell line

The epithelial cell line from the dipteran Chironomus tentans responds to the insect steroid hormone 20-hydroxyecdysone and the non-steroidal analogue tebufenozide by undergoing a morphogenetic and biochemical differentiation program. Long-term culture in the presence of 20-hydroxyecdysone has resulted in the selection of subclones that are resistant to the steroid but respond normally to the non-steroidal analogue. In the present study, several subclones that were resistant to the steroid hormone have been compared with steroid-sensitive subclones with respect to their capability to metabolize 20-hydroxyecdysone. Homogenates of both types of cells, when incubated with 3H-labelled steroid in the presence of NADPH, producecd 20,26-dihydroxyecdysone, which was further metabolized to two compounds, which behaved less polar than 20-hydroxyecdysone on reverse-phase HPLC. Ecdysone, a less-active hormone precursor, provided 26-hydroxyecdysone as the only product. The metabolites were identified by mass spectrometry coupled to HPLC, chromatography with authentic samples, and formation of acetonides. The structure of 20,26-dihydroxyecydsone was confirmed by 1H-NMR. The enzyme responsible for the synthesis of 20,26-dihydroxyecdysone in the Chironomus cell preparations has been characterized as a typical cytochrome P-450-dependent monooxygenase. It was a strictly microsomal enzyme, sensitive to inhibition by carbon monoxide and imidazole/triazole-based fungicides, and required NADPH for maximal activity. NADH could partly replace NADPH. The Michaelis constant (Km) for 20-hydroxyecdysone was 0.96 microM, and the maximal enzyme velocity (Vmax) was 50 pmol substrate metabolized x mg protein(-1) x min(-1). 26-Hydroxylation of 20-hydroxyecdysone was inhibited by ecdysone, an alternative substrate, and by inokosterone, a product analogue, to 50% at 1.4 microM and 0.73 microM, respectively. When various subclones were compared with respect to their in vitro rate of 20-hydroxyecdysone metabolization, those clones known to be resistant to the steroid were 'high metabolizers' (> 70% relative rate), whereas the sensitive clones were 'poor metabolizers' (< 30% relative rate). Hence, it is tempting to conclude that ecdysteroid resistance of the Chironomus cell clones is due to metabolic inactivation of the steroid hormone.

Isolation of mitochondrial porin of the fly Protophormia: porin modification by the pesticide CGA 140'408 studied in lipid bilayer membranes

Mitochondrial porin from the fly Protophormia was solubilized with detergent from whole mitochondria and purified by chromatography across a hydroxyapatite (HPT) column. The purified protein had an apparent molecular mass of about 30 kDa on SDS-PAGE. Partial sequencing of the protein confirmed that it is porin. When reconstituted in planar lipid bilayer membranes, porin formed ion-permeable channels with single-channel conductances of 2.4 and 4.5 nS in 1 M KCl. At low voltage, Protophormia porin displayed the properties of a general diffusion pore and had a small selectivity for anions over cations. At transmembrane potentials starting with about 20-30 mV, the channel switched in closed state, which is still ion-permeable. Our results suggest that Protophormia porin possesses functional properties similar to those of other mitochondrial porins. Porin was also isolated and purified from mitochondria, which were treated with the carbodiimide CGA 140'408 It represents the active derivative of diafenthiuron a new acaricide and insecticide. This carbodiimide labels both a F0-component of the inner membrane ATPase and outer membrane porin in a similar way as N,N'-dicyclohexylcarbodiimide (DCCD). Reconstitution experiments with the CGA 140'408-modified porin showed no significant effect of the modification on the single-channel conductance, suggesting that CGA 140'408 binds outside the channel. The voltage-dependence of the CGA 140'408-modified porin was changed with respect to the unmodified form. The closed configuration of the pesticide-modified channel was reached at smaller transmembrane potentials, suggesting a shift of the open to the closed state of Protophormia porin by pesticide binding. A possible contribution of this effect to the pesticide action is discussed.

Stimulation of human peripheral blood lymphocytes by bioactive peptides derived from bovine milk proteins

The in vitro modulation of the proliferation of human peripheral blood lymphocytes by different synthetic peptides derived from milk proteins was investigated. Therefore, proliferation changes were followed up after incorporation of BrdU into the DNA, and the influence on protein biosynthesis was measured using the [3H]leucine incorporation test. Tyr-Gly and Tyr-Gly-Gly significantly enhanced (maximal 90 and 35%, respectively) the proliferation of PBL. For beta-casomorphin-7 and beta-casomorphin-10,lymphocyte proliferation was suppressed at lower concentrations, but stimulated at higher concentrations (> or = 10(-7) mol/l). Protein synthesis was stimulated (maxima at 25%) only with Tyr-Gly and Tyr-Gly-Gly. The findings point to a need for further studies on the possible function of peptides derived from milk proteins as orally bioavailable immunopotentiatory compounds.

Biosynthetic modulation of sialic acid-dependent virus-receptor interactions of two primate polyoma viruses

Sialic acids are essential components of the cell surface receptors of many microorganisms including viruses. A synthetic, N-substituted D-mannosamine derivative has been shown to act as precursor for structurally altered sialic acid incorporated into glycoconjugates in vivo (Kayser, H., Zeitler, R., Kannicht, C., Grunow, D., Nuck, R., and Reutter, W. (1992) J. Biol. Chem. 267, 16934-16938). In this study we have analyzed the potential of three different sialic acid precursor analogues to modulate sialic acid-dependent virus receptor function on different cells. We show that treatment with these D-mannosamine derivatives can result in the structural modification of about 50% of total cellular sialic acid content. Treatment interfered drastically and specifically with sialic acid-dependent infection of two distinct primate polyoma viruses. Both inhibition (over 95%) and enhancement (up to 7-fold) of virus binding and infection were observed depending on the N-acyl substitution at the C-5 position of sialic acid. These effects were attributed to the synthesis of metabolically modified, sialylated virus receptors, carrying elongated N-acyl groups, with altered binding affinities for virus particles. Thus, the principle of biosynthetic modification of sialic acid by application of appropriate sialic acid precursors to tissue culture or in vivo offers new means to specifically influence sialic acid-dependent ligand-receptor interactions and could be a potent tool to further clarify the biological functions of sialic acid, in particular its N-acyl side chain.

New amino sugar analogues are incorporated at different rates into glycoproteins of mouse organs

Different radiolabelled N-acyl-derivatives of D-glucosamine were synthesized using D-glucosamine and the respective carbonic acid anhydride. Metabolism of these sugar analogues could be shown in vitro as well as in vivo. After the intraperitoneal administration of these radiolabelled N-acyl-D-glucosamines to mice, their rate of incorporation into glycoproteins of different organs was found to increase markedly with the length of the N-acyl side chain. Highest incorporation was measured in the whole intestine using N-pentanoyl-D-glucosamine as label.

Biosynthesis of a nonphysiological sialic acid in different rat organs, using N-propanoyl-D-hexosamines as precursors

In this study it could be shown that in rat the normally occurring N-acetyl neuraminic acid can be modified in its N-acyl moiety by in vivo administration of the chemically synthesized N-propanoyl precursors, N-propanoyl-D-glucosamine or N-propanoyl-D-mannosamine. It could be shown that each of these nonphysiological amino sugar analogues was incorporated into both membrane and serum glycoproteins. After treatment of rats with radiolabeled N-[acyl-1-14C]D-mannosamine, radioactivity could be removed from serum glycoprotein fractions by incubation with neuraminidase from Clostridium perfringens or from Arthrobacter ureafaciens. Mild acid hydrolysis removed 98% of the radioactivity after in vivo labeling with N-[acetyl-1-14C]D-mannosamine and 86% after labeling with N-[propanoyl-1-14C]D-mannosamine. Chromatographic analysis yielded two compounds, i.e. N-acetyl neuraminic acid and N-propanoyl neuraminic acid, the latter being identified by gas liquid chromatography/mass spectrometry studies. Measurement of protein-bound radioactivity in different rat organs revealed a different organotropy of the natural and the nonphysiological neuraminic acid precursor. Of the glucosamine derivatives, N-acetyl-D-glucosamine showed the higher rate of uptake and incorporation in most organs (except in the submandibulary gland), and especially in kidney cortex and Morris hepatoma 7777. Natural and the unphysiological mannosamine derivatives were incorporated at similar rates, except in liver, where N-acetyl-D-mannosamine was taken up and metabolized more effectively. This finding indicates that it is possible to modify the acyl group of N-acetyl neuraminic acid in vivo by the introduction of an N-propanoyl group and possibly other homologous N-acyl groups. This procedure may provide a tool for a further characterization of the biological function of sialic acids.

Incorporation of N-acyl-2-amino-2-deoxy-hexoses into glycosphingolipids of the pheochromocytoma cell line PC 12

The synthesis of N-acyl-2-amino-2-deoxy-hexoses, their metabolism and their incorporation into glycosphingolipids of rat pheochromocytoma cell line PC 12 were investigated. The data indicate that in PC 12 cells the N-acyl-2-amino-2-deoxy-hexoses, N-propanoyl-D-glucosamine and N-butanoyl-D-glucosamine are metabolized to the corresponding phosphates, and that N-propanoyl-D-glucosamine is also metabolized to N-propanoyl neuraminic acid. Using variously radiolabelled N-acyl-2-amino-2-deoxy-hexoses, their incorporation into glycosphingolipids was shown.

Effects of tachykinins on myenteric neurones of the guinea-pig gastric corpus: involvement of NK-3 receptors

Responses of gastric myenteric neurones evoked by the mammalian tachykinins substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) were investigated using conventional intracellular recording methods. Application of the tachykinins caused a long lasting depolarization of the membrane potential which was associated with increased spike discharge and augmented excitability of the cells. The responses slowly desensitized. Additionally, cross desensitization occurred between SP, NKA and NKB. Both the NK-1 receptor agonist [Sar9,MetO2(11)]SP and the NK-2 receptor agonist [beta-Ala8]NKA(4-10) had no effect on the electrical properties of the neurones. Only the NK-3 receptor agonist [MePhe7]NKB mimicked the excitatory response observed during SP, NKA and NKB applications. [MePhe7]NKB-induced desensitization abolished the response to SP, NKA and NKB. However, long lasting applications of [Sar9,MetO2(11)]SP or [beta-Ala8]NKA(4-10) had no effect on the SP, NKA or NKB responses. The excitatory effect of SP, NKA and NKB remained unchanged during application of the tachykinin analogues [D-Arg1,D-Trp7,9,Leu11]SP and [Tyr5,D-Trp6,8,9,Arg10]NKA(4-10). The results indicate that SP, NKA and NKB act as excitatory neuromodulators within the enteric nervous system of the stomach. The effects of SP, NKA and NKB appeared to be mediated by activation of NK-3 receptors.

[Identification of human porins. I. Purification of a porin from human B-lymphocytes (Porin 31HL) and the topochemical proof of its expression on the plasmalemma of the progenitor cell]

We describe for the first time a porin (Porin 31HL) on the plasmalemm of an eukaryontic cell line, where porins have been found only on the outer mitochondrial membranes. The expression of the porin on the plasmalemm of transformed human B-lymphocytes is demonstrated by cytotoxicity- and indirect immunofluorescence techniques with living and fixed cells. The rabbit xenoantisera used were directed against purified Porin 31HL and free or acetylated synthetic peptides of its nineteen N-terminal amino acids. The three-step purification procedure for Porin 31HL started from a total membrane fraction of the B-cell line, followed by ion-exchange chromatography on CM- and DEAE-cellulose and a final gel filtration in SDS on Sephacryl S-300.

[Identification of human porins. II. Characterization and primary structure of a 31-lDa porin from human B lymphocytes (Porin 31HL)]

We characterize and describe for the first time the primary structure of a human porin with the molecular mass of 31 kDa derived from the plasmalemm of B-lymphocytes (Porin 31HL). Porin 31HL is shown to be a basic, channel forming membrane protein. The protein chain is composed of 282 amino acids with a relative molecular mass of 30641 Da without derivatisation. It is not a glycoprotein. The N-terminus is acetylated. Altogether the amino-acid sequence shows 56% hydrophilic or charged amino acids arranged in alternating regions of hydrophilic or hydrophobic character as it is typical for porins. In addition the 18 N-terminal amino acids of Porin 31HL can be arranged to an amphilic alpha-helix like in other porins. Porin 31HL shows approx. 29% or 24% identity to the primary structure of mitochondrial porins of Neurospora crassa and Saccharomyces cerevisiae. Partial data on mitochondrial porins from rat kidney and beef heart show sequence identity of about 90% to the human B cell porin elaborated here.

The complete amino-acid sequence of the bilin-binding protein from Pieris brassicae and its similarity to a family of serum transport proteins like the retinol-binding proteins

The amino-acid sequence from the bilin binding protein (BBP) of the butterfly Pieris brassicae has been determined. The apoprotein with a length of 173 amino-acid residues has a molecular mass of 19,676 Da. The sequence analysis was performed by automated Edman degradation of the intact apoprotein and of fragments as large as possible generated from different digestions. The 3-dimensional structure of BBP, determined by Huber et al. (Huber, R., Schneider, M., Epp, O., Mayr, I., Messerschmidt, A., Pflugrath, J. & Kayser, H. (1987) J. Mol. Biol. 195, 423-434 and Huber, R., Schneider, M., Mayr, I., Müller, R., Deutzmann, R., Suter, F., Zuber, H., Falk, H. & Kayser, H. (1987) J. Mol. Biol. 198, 499-513) down to 2-A resolution, exhibits a similar conformation to the human retinol binding protein. Sawyer (Sawyer, L. (1987) Nature (London) 327, 659) demonstrated that proteins from a wide variety of sources can be gathered into a "superfamily". Computer searches of data banks yielded in a new member of this superfamily, namely human alpha 1-acid glycoprotein. One of the functions of the listed proteins is to bind and transport small hydrophobic molecules in serum.

Molecular structure of the bilin binding protein (BBP) from Pieris brassicae after refinement at 2.0 A resolution

The bilin binding protein (BBP) from the insect Pieris brassicae has been analysed for amino acid sequence, spectral properties and three-dimensional structure. The crystal structure that had been determined by isomorphous replacement has been refined at 2.0 A (1 A = 0.1 nm) resolution to an R-value of 0.20. The asymmetric unit contains four independent subunits of BBP. The co-ordinate differences are 0.25 A, in accord with the estimated error in co-ordinates. The polypeptide chain fold is characterized by an eight-stranded barrel. The connecting loops splay out at the upper end of the barrel and open it, whilst the lower end is closed. The overall shape resembles a calyx. The biliverdin IX gamma chromophore is located in a central cleft at the upper end of the barrel. The bilatriene moiety is in cyclic helical geometry with configuration Z,Z,Z and conformation syn,syn,syn. The geometry is in accord with the spectral properties and permits a correlation between sign of the circular dichroism bands and sense of the bilatriene helices. The fold of BBP is related to retinol binding protein (RBP), as had been recognized in the preliminary analysis, although the amino acid sequences of RBP and BBP show only 10% homology. There are large differences in the loops at the upper end of the barrel, whilst the segments of the centre and the lower end of the barrel superimpose closely. The ligands of BBP and RBP, biliverdin and retinol, respectively, are also similarly located.

Crystallization, crystal structure analysis and preliminary molecular model of the bilin binding protein from the insect Pieris brassicae

The bilin binding protein of the butterfly Pieris brassicae has been prepared, crystallized and its crystal structure determined at high resolution using film and FAST area detector intensity data. The crystallographic asymmetric unit contains a tetramer of identical subunits with a molecular weight of about 90,000. The crystal structure was determined by isomorphous replacement. Use was made of the molecular symmetry to improve phases. A molecular interpretation of the electron density distribution and partial tracing of the polypeptide chain was possible without amino acid sequence information, as the fold is very similar to retinol binding protein. It is characterized by a beta-barrel formed by two orthogonal beta-sheets and an alpha-helix. The bilin pigment seems to be bound within the beta-barrel analogously to retinol in retinol binding protein. The tetramer in the crystal has C2 symmetry and is a dimer of dimers of quasi-equivalent subunits.

[Is the HLA-DR associated glycoprotein p31 a ubiquitous molecule?]

The glycoprotein p31 (also called Ii, In, M1, Dr gamma, XM 1) has been shown up to now only in the membranes of B lymphocytes as well as of epidermal and endothelial cells, where it is always accompanied by antigens of the HLA-DR type. It is therefore called HLA-DR-associated protein. As we show here, the membranes of muscle, liver and brain contain protein molecules with the relative molecular mass Mr = 31 000-33 000 and an isoelectric point around 7.5. These parameters correspond to those of the p31 of B lymphocytes. These molecules, as well as the p31 of B lymphocytes, can be concentrated by ion exchange chromatography. In two-dimensional electropherograms they are identical to those of B lymphocytes. It can therefore be assumed that the po 31 is not really associated with the HLA-DR antigens but is a ubiquitous molecule.

Metabolic clearance rates of catechol estrogens in rats

MCRs of the catechol estrogens 4-hydroxyestradiol (4-OHE2) and 2-hydroxyestradiol (2-OHE2) and of the parent estrogen 17 beta-estradiol (E2) were determined in rats. Long term ovariectomized Wistar rats were infused with the steroids at a constant rate for 3 days via a catheter placed in the abdominal aorta. Blood samples were drawn discontinually by retroorbital puncture, and the serum concentrations of E2, 4-OHE2, and 2-OHE2 were measured by RIA. Steady state was reached within 24 h of infusion. Mean serum MCRs were calculated to be 740 +/- 117 ml/h for E2, 2700 +/- 1000 ml/h for 4-OHE2, and 8300 +/- 1700 ml/h for 2-OHE2. Thus, the MCRs of the catechol estrogens were definitely higher than the MCR of E2 resulting in an apparent ratio of 1:4:11 (E2:4-OHE2:2-OHE2).

[Identification of beta, beta-caroten-2-ol and beta, beta-carotene-2,2'-diol in the stick insect, Carausius morosus Br.; a reinvestigation study]

Two major carotenoids of the stick insect were reinvestigated and shown to be beta,beta-caroten-2-ol and beta,beta-carotene-2,2'-diol and not isocryptoxanthin (beta,beta-carotin-4-ol) and isozeaxaanthin (beta,beta-carotene-4,4'-diol). Both pigments are esterified with fatty acids. The identification is based on cochromatography with authentic 2-, 3- and 4-isomers of the mono- and dihydroxy pigment, mass spectra, and chemical behaviour. In acid solution beta-beta-carotene-2,2'-diol is specifically dehydrogenated and rearranged to ketones with retro structures in analogy to the reactionof beta,beta-caroten-2-ol as recently reported. The final product of the diol is 4,5-dihydro-4,5'-retro-beta,beta-carotene-2,2'-dione. This is the first demonstration of beta,beta-carotene-2,2'-diol in an animal.

Isolation of beta, beta-caroten-2-ol from an insect, Cerura vinula (Lepidoptera)

The monohydroxy carotenoid from the moth Cerura vinula has been shown to be beta, beta-caroten-2-ol on the basis of electronic, infrared, proton magnetic-resonance, and mass spectra. On acid treatment in the presence of molecular oxygen this carotenoid is dehydrogenated to 4',5-retro-beta,beta-caroten-2-one. The identification of beta,beta-caroten-2-ol by its retro product, its time course of acetylation, and its chromatographic properties relative to beta,beta-caroten-3-ol and beta,beta-caroten-4-ol is discussed. This is the first demonstration of a 2-hydroxylated carotenoid in an insect. Implications on the biogenesis of this pigment are considered.